Why use thermocouples to measure concrete temperature?

Monitoring the concrete temperature can give useful insight about the curing. First of all, you can reduce problems with overheating concrete (often seen in large concrete structures, also called mass concrete) and a too large temperature gradient can occur might lead to cracks in the finished concrete structure. This cracks breaks the concrete surface and serves as channels for chlorides to the reinforcing steel (rebar) and course damage.

The other benefit of monitoring the concrete temperature is to follow the curing process/maturity of the concrete. If you have made a calibration of the concrete mix, you will be able using the maturity method with high precision tell something about the concrete strength during the concrete curing.

So in other words too high temperatures can cause:

  • Increased water use and thereby added costs
  • Increased shrinkage leading to cracks in concrete
  • Lower final concrete strength
  • Potential corrosion attack on reinforcements due to chloride attacks

To be able to control the heating in the concrete, you need to measure and monitor the process. This can be done by using thermocouples – an inexpensive solution and widely available.
A thermocouple is simply attached to the rebar/reinforcement before pouring the concrete and then connected to a data logger or a wireless sensor like the Orbit K.

In larger structures, you will often measure at several depths at each point to make sure the temperature gradient across the concrete does not exceed the safety limit.

Benefits of using thermocouples for concrete monitoring:

  • Affordable method of measuring concrete (only losing the inexpensive cable)
  • Acceptable and available worldwide
  • An acceptable method for leading international standards for concrete curing (ex. ASTM1070)
  • Can be installed and configured quickly
  • Flexible in lengths

For monitoring the early age strength in concrete you might monitor the temperature with 10 minutes intervals because of the high-temperature changes/variations over a short period of time. While concrete curings over 7-10 days you might only need data every hour.